Spring onions are one of the easiest and quickest crops you can grow on an allotment. They take up very little space, grow well in cool conditions, and can be harvested at almost any stage, making them ideal for beginners and experienced growers alike.
They’re perfect for filling gaps between slower-growing crops and can be sown successionally to provide a steady harvest over many months.
When to Sow Spring Onions
Spring onions can be sown for most of the year, depending on where they’re grown.
Early sowings can be made under cover from late winter, while outdoor sowing usually starts in early spring once the soil begins to warm. Successional sowing every few weeks will ensure a continuous supply rather than one large harvest.
Autumn sowings are also possible with hardy varieties, which can overwinter and provide an early crop the following spring.
Where to Grow Spring Onions
Spring onions grow best in an open, sunny position but will tolerate light shade. They are well suited to allotments, raised beds, containers, and even window boxes.
They prefer free-draining soil that hasn’t been freshly manured. Rich soil encourages leafy growth, but too much nitrogen can reduce flavour and increase the risk of disease.
Because they don’t form large bulbs, spring onions don’t need deep soil and can be grown in relatively shallow beds.
How to Sow Spring Onions
Spring onions are usually grown directly from seed.
Prepare the soil by removing weeds and raking it to a fine tilth. Sow seeds thinly in shallow drills around 1cm deep, spacing rows about 15cm apart. Lightly cover with soil and water gently.
There’s no need to thin heavily, as spring onions are harvested young, but overcrowding can result in thinner stems. If seedlings emerge too closely together, thin lightly or harvest some early as baby onions.
Caring for Spring Onions
Spring onions are low-maintenance, but a few simple steps will improve results.
Keep the soil consistently moist, especially during dry spells, as drought stress can cause the plants to bolt prematurely. Regular watering is more important than feeding, although a light general fertiliser can be applied if growth is slow.
Weeding is important early on, as young spring onions can be easily outcompeted by weeds. Once established, they require very little attention.
Harvesting Spring Onions
Spring onions can be harvested at almost any size, usually from around 8 weeks after sowing.
Pull them gently from the soil once they reach the thickness you prefer. Smaller onions are milder and more tender, while larger ones have a stronger flavour.
If you’ve sown thickly, harvesting some early will naturally thin the remaining plants and allow them more space to grow.
How Long Do Spring Onions Take to Grow?
Most spring onions are ready to harvest within 8–12 weeks of sowing, depending on conditions and variety.
Overwintered crops may take longer but will provide an earlier harvest in spring when little else is available.
Because they grow quickly, spring onions are ideal for succession sowing throughout the growing season.
Common Problems When Growing Spring Onions
Spring onions are generally trouble-free, but a few issues can occur.
Bolting can happen in hot, dry conditions or if plants are stressed. Regular watering helps reduce this risk. Onion fly can occasionally be a problem, although it’s far less common than with bulb onions. Using fine mesh netting can help prevent this.
Yellowing leaves are often a sign of water stress or poor soil conditions rather than disease.
Crop Rotation and Companion Planting
Spring onions fit well into most crop rotation plans because they’re quick growing and shallow rooted. They can be used as a follow-on crop after early potatoes or salad crops.
They’re also useful as companion plants, as their scent may help deter some pests when grown alongside carrots, lettuce, or beetroot.
Avoid planting them repeatedly in the same spot year after year to reduce the risk of soil-borne issues.
Growing Spring Onions on an Allotment
On an allotment, spring onions are best treated as a flexible filler crop. They’re ideal for planting in spare corners, along bed edges, or between slower-growing vegetables.
Because they’re quick to mature and easy to grow, they’re also a great crop for trying out new layouts or testing soil conditions before committing to longer-term planting.
Are Spring Onions Worth Growing?
Spring onions are one of the most reliable crops you can grow on an allotment. They’re fast, productive, and versatile, and they make excellent use of space that might otherwise be left empty.
With regular sowing and minimal care, you can harvest fresh spring onions for much of the year, making them a staple crop for allotment growers of all experience levels.